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  • 2000-2004  (3)
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Material
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Analytical fractionation of aquatic humic substances by metal affinity chromatography on iron(III)-coated cellulose (2000)
    Springer
    Fresenius' journal of analytical chemistry 366 (2000), S. 95-101 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chromatographic fractionation of aquatic humic substances (HS) onto iron(III)-coated cellulose (Cell-Fe(III)) as a metal-loaded adsorbent is described, analogously to the separation principle of the well-established metal affinity chromatography (MAC). For that purpose the sorption of HS from different aquatic origin on that collector was characterized by their kinetics and equilibrium distribution coefficients Kd. Based on Kd values of 103 to 104,mL/g, and fast sorption kinetics a preparative HPLC procedure, using stepwise increased pH-values (pH 8–12.5, borate buffer) as an eluent, was developed for the fractionation of dissolved HS (up to 7 fractions of different amount). The fractions obtained by this MAC procedure from selected aquatic HS samples were different in their Cu(II) complexation capacity, absorbance ratio E265 nm/E365 nm and Fourier transform infrared spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050017
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of aquatic humic substances and their metal complexes by immobilized metal-chelate affinity chromatography on iron(III)-loaded ion exchangers (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 689-696 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The analytical fractionation of aquatic humic substances (HS) by means of immobilized metal-chelate affinity chromatography (IMAC) on metal-loaded chelating ion exchangers is described. The cellulose HYPHAN, loaded with different trivalent ions, and the chelate exchanger Chelex 100, loaded to 90% of its capacity with Fe(III), were used. The cellulose HYPHAN, loaded with 2% Fe(III), resulted in HS distribution coefficients Kd of up to 103.7 mL/g at pH 4.0 continuously decreasing down to 101.5 at pH 12, which were appropriate for HS fractionation by a pH-depending chromatographic procedure. Similar distribution coefficients Kd were obtained for HS sorption onto Fe(III)-loaded Chelex 100. On the basis of Fe-loaded HYPHAN both, a low-pressure and high-pressure IMAC technique, were developed for the fractionation of dissolved HS applying a buffer-based pH gradient for their gradual elution between pH 4.0 and 12.0. By coupling the Chelex 100 column under high-pressure conditions with an inductively coupled plasma mass spectrometer an on-line characterization of HS metal species could be achieved. Using these fractionation procedures a number of reference HS were characterized. Accordingly, the HA (humic acids) and FA (fulvic acids) studied could be discriminated into up to 6 fractions by applying cellulose HYPHAN, significantly differing in their Cu(II) complexation capacity but hardly in their substructures assessed by conventional FTIR. In the case of using Chelex 100 exchanger resin two major UV active HS fractions were obtained, which significantly differ in their complexation properties for Cu(II) and Pb(II), respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000565
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Structural and elemental investigations of isolated aquatic humic substances using X-ray photoelectron spectroscopy (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 274-280 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural and elemental investigations of aquatic humic substances (HS) by means of X-ray photoelectron spectroscopy (XPS) are described. For that purpose small amounts (10–50 μg) of dissolved reference HS, which were characterized within the German research program DFG-ROSIG, were dried as thin films on small pieces of a high-purity silicon wafer. The photoelectrons from such HS layers exhibited characteristic signals of carbon C1s, nitrogen N1s, oxygen O1s and sulfur S2s, which could be fitted by Gaussian curves and used for the quantification of various moieties of HS: carbon (C-C, C-O, C=O, O=C-O), oxygen (C-O, C=O), nitrogen (C-N, C-N+) and sulfur. Moreover, by adding up the element signals of the HS samples their elemental composition of C, O, N and S was assessed. A comparison of the data based on solution state NMR and conventional elementary analysis revealed a satisfactory accuracy with those obtained by XPS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000492
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    Paper (German National Licenses)
    Fulltext
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